1. Field of this Invention
This ivnention relates to a process for the production of closed-cell, extra soft polyvinyl chloride foam plastics having improved volume stability at higher temperatures, from polyvinyl chloride or vinyl chloride copolymerizates, containing plasticizers and foaming agents, in the form of plastigels and plastisols.
2. Prior Art
It has been known to produce foam plastics from thermoplastic plastics in a first step, by heating plastic plastigels or plastisols, containing foaming agents and plasticizers, in pressure molds to temperatures of 150.degree. to 180.degree. C. for the purpose of gelling and decomposition of foaming agents, cooling subsequently to 20.degree. to 80.degree. C., and, in a second step, expanding by heating without pressure the crude foam plastic removed from the pressure molds.
The disadvantage of the products obtained according to such a process that one will indeed obtain soft, but taut, i.e., little flexibility, foam plastics, the volume stability of which, particularly for use in life jackets and bodies with buoyancy, leaves much to be desired. The shrinkage which occurs when such products are stored for seven days at 60.degree. C. is about 8 to 20 percent.